This patch introduces JOBCTL_PENDING_MASK and replacestask_clear_jobctl_stop_pending() with task_clear_jobctl_pending()which takes an extra @mask argument.

JOBCTL_PENDING_MASK is currently equal to JOBCTL_STOP_PENDING butfuture patches will add more bits. recalc_sigpending_tsk() is updatedto use JOBCTL_PENDING_MASK instead.

task_clear_jobctl_pending() takes @mask which in subset ofJOBCTL_PENDING_MASK and clears the relevant jobctl bits. IfJOBCTL_STOP_PENDING is set, other STOP bits are cleared together. Alltask_clear_jobctl_stop_pending() users are updated to calltask_clear_jobctl_pending() with JOBCTL_STOP_PENDING which isfunctionally identical to task_clear_jobctl_stop_pending().